I'm trying to make a basic mould using brush-on latex.
For some reason I'm having trouble with it curing. Even one thin coat (1-3mm) is taking about 3 days to dry fully. at this rate it'll be months to make a decent mould.
I've tried thickener but it just gums up. what can I do?
Brush-on latex wont work properly. In fact, when you brush more on, it sometimes re-dissolves the already dried latex underneath. It's not really good enough to make a decent mold with. You need to use some real RTV rubber. I use a fantastic product called Pinkysil which does not embed many bubbles, and catalyses within half an hour.
Its better to use silicon actually, latex molds will blow after a few pulls, and depending on what medium you intend to cast with, details rapidly can come off with each part run.. of course the molds I am redoing are 20-plus years old I am redoing all my latex molds with J. Greer silicon. From what I have seen, latex is a natural rubber product that naturally degrades over time.
I Spoke with John at length about brushing on both Silicon and latex. The color is added by the manufacturer to conceal the bubbles. Brushing on a thin layer to the part, allowing one hour from mixing (including time brushing on), then putting the part in the mother mold with the rest of the silicon, this allows time to still achieves a true chemical bond.
I hope this helps.
What brand of latex are you using? Is it pre-thickened or the rather watery stuff?
Heat and airflow are generally helpful in the curing process, but not too much heat as that'll mess up the latex. One layer should be dry in about 15 minutes. Not really sure what could be going wrong.
That's the only way latex will work,it works by air drying.You have to apply it in thin applications.If you apply some additionl heat with a hair dryer or maybe a heat gun(without cooking it) it will cure faster.I'd never use it,but I suppose maybe some applications it is necessary?Your'e better off with an RTV silicone.Latex is really only good for casting with plaster/hydrocal products...DO NOT use it for a urethane resin,epoxy of pollyester.You can,but your'e lucky if you get one good pull out of it and you have to use a really strong release agent.
Last edited by JPolacchi; Mar 16, 2009 at 1:08 PM. Reason: type-O's
I think he is pouring/brushing the layers on too thick and there is no "airflow".It may also be too cold so the latex takes longer to set and cure?Chiok said:
I was brushing thin coats on at room temp. But it's just not working out.
Is it a glove mold or being brushed into a cavity?How long have you had the latex,or how long was it sitting in the store?Does it have a date on it?Liquid latex will break down,and it also depends how it was stored,or possibly even how it was shipped before it arrived to its destination.If its old,that may be a major factor and could explain why its not curring?If you are brushing it into a cavity,that might also be a reason why its not curing(although i doubt it),otherwise...I'm out of answers.Try putting a hair dryer on it (on low heat).
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